Anti-nuclear campaigners staged an alternative birthday party yesterday to "commiserate" over the 30th birthday of Somerset's Hinkley B nuclear power station. As they gathered around a mock-up of the power station in the garden of campaigner Jim Duffy, they said their dearest birthday wish was to see the plant closed down.

It has had a controversial history, including claims in 2002 that a five-year survey of four types of cancer showed a significantly higher than expected level in electoral wards nearby. Later that year, Parents Against Hinkley conducted a doorstep survey of a third of homes in Burnham-on-Sea and said breast cancer incidence was three times higher than normal, and leukaemia was double.

In 2003, Somerset Coast Primary Care Trust commissioned a cancer study that showed breast cancer in four wards from Brean to Highbridge was 24 per cent higher, over a 10-year period, than expected. But they said this could not be proved to be connected to Hinkley.

In December 2004, three or four cracks were found in the graphite core of the reactor. Such cracks have been known to occur at other plants.

Stop Hinkley said these cracks could prevent control rods being used in an emergency and create a local "fuel-fire" that could escalate. Mr Duffy said: "We very much regret the 30 years this plant has been running with its ongoing radioactive discharges and production of highly dangerous plutonium. Now is the time to shut this plant, move on to renewable energy and wave goodbye to the nuclear era." Nuclear power is being supported by some as the solution to the growing energy crisis.

British Energy runs 11 plants. Yesterday a spokesman for the company said: "We will be looking to extend the life of our plants where appropriate." He said the issue of the cracks was a matter for the Nuclear Regulator "but if there was an issue we would be closed".